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Abstract

This thesis focus on the carbon and oxygen fluxes in the Barents and Norwegian Seas
and presents four studies where the main topics are variability of biological
production, air-sea exchange and budget calculations.
The world ocean is the largest short term reservoir of carbon on Earth, consequently it
has the potential to control the atmospheric concentrations of carbon dioxide (CO2)
and has already taken up ~50 % of the antropogenically emitted CO2. It is thus
important to study carbon related processes in the ocean to understand their changes in
the past, present, and future perspectives. The main function of the Arctic
Mediterranean, within which the study area lies, in the global carbon cycle is to take
up CO2 from the atmosphere and, as part of the northern limb of the global
thermohaline circulation, to convey surface water to the ocean interior.
A carbon budget is constructed for the Barents Sea to study the carbon fluxes into and
out of the area. The budget includes advection, air-sea exchange, river runoff, land
sources and sedimentation. The results reviel that ~5.6 Gt C annually is exchanged
through the boundaries of the Barents Sea mainly due to advection, and that the carbon
sources within the Barents Sea itself are larger than the sinks. The change in carbon
content of the Atlantic Water as it passes through the Barents Sea is investigated,
revieling that ~0.030 Gt C is taken up from the atmosphere and exported to the Arctic
Ocean during one year. The main part of the increased carbon content is channelled
through biological production.
Spatial and interannual variability of biological production and air-sea exchange is
investigated in the north-western Barents Sea during the spring-summer season,
interannual variability of oxygen and carbon fluxes due to biological production is also
studied at Ocean Weather Station M in the Norwegian Sea. Both the spatial and
interannual variability in the Barents Sea depend on the distribution of water masses
and sea ice cover while the causes behind the variability at Ocean Weather Station M
are more complex. Air-sea exchange was also studied in the Storfjorden polynya
where it was discovered that formation of sea ice during winter is accompanied by a
large air-sea CO2 exchange.